Local coils are currently often used in modern magnetic resonance systems/magnetic resonance devices. Local coils have the advantage that they can be arranged closer to the target area to be recorded and therefore provide an improved signal-to-noise ratio (SNR). Furthermore, parallel imaging techniques can be employed by using a plurality of receiving coil elements.
The handling of the local coils itself is a time-consuming step in the workflow of a magnetic resonance examination in the field of use of local coils. Local coils to be used must firstly be selected by an operator, then be correctly arranged on the patient and be connected to a terminal, which is usually provided in the patient couch. This is complex in particular if it is taken into account that different local coils, which are adapted in terms of construction to the respective purpose, are used for different examinations and for different regions of the body to be examined.
A further problem in modern magnetic resonance devices is patient comfort. Due to the confined spaces patients who in particular are assessed as being claustrophobic, exhibit fear reactions and by way of example movements and the like which can lead to a poor image quality and to a termination of the examination. Local coils that have to be arranged close to the patient can intensify this problem still further since a patient can feel constricted by the close-fitting local coils.
A further problem in connection with the local coils is that slight damage can occur as a result of their manual positioning and manual conveying, by way of example if the local coils fall out of an operator's hand. Without local coils specifically matched to the magnetic resonance device problems may also occur if local coils become jammed between the patient and the patient-receiving device. Finally, the local coils that are not going to be used and are to be positioned at a distance from the magnetic resonance device require a certain amount of storage space. If this is to be provided in the magnetic resonance space itself, then an appropriate design thereof should be provided.
Finally, there is also the problem in relation to local coils of the sterility requirements in image-guided interventions which can limit the use of magnetic resonance systems for processes of this kind, or at least render them very time-consuming. The local coils also limit access to the patient which is often necessary for carrying out interventions.
Methods have already been proposed in for solving these problems. A receiving coil system is therefore known by way of example from DE 10 2012 206 920 A1 in which a holding device for positioning the receiving coils is used, wherein the holding device is positioned on a patient table and wherein the receiving coils are pivotably secured to the patient table. With the aid of the holding device the local coils can be adjusted to the respective patient, i.e. the dimensions of the body of the patient, and the respective examination, in particular the region of the body to be examined. It is possible to position the receiving coils in such a way that the patient feels less constricted, in particular the local coils can be arranged at a distance from the patient therefore, so while there may be losses in the quality of the generated image data and/or an extension to the length of the examination, anxiety attacks in the patient may be avoided. Securing the local coils to the receiving table also has the advantage that they cannot slide out of the operator's hand and fall to the floor. Specifically, a multi-stage adjusting mechanism is also proposed there with which the receiving coils (local coils) are shifted from a park position into a pivoting position, then turned by a pivoting movement about a first pivot axis and oriented toward a patient positioned on the patient table. The local coils disclosed therein can preferably be adjusted to the surface shape of the region of the body of the patient. This adjustment can be automated, for which purpose the local coils can comprise distance sensors with the aid of which the distance between the receiving coil and the patient may be metrologically detected. The local coil can then be automatically and preferably completely automatically oriented relative to the body of the patient on the basis of predefined distance parameters. A value or a value range can be specified for the signal-to-noise ratio as the desired value for an automated adjustment, with a value between 20 and 30 having been proven to be advantageous.
DE 10 2012 206 921 B3 discloses a similar concept, according to which a holding device for adjustable positioning of the receiving coils is likewise provided which comprises at least one rail which is positioned on a patient table and along which the receiving coils can be pushed. Also disclosed therein is that the receiving coil can be adjusted to the surface shape of the region of the body of the patient, with an automated adjustment, as already described, being possible.
DE 10 2012 206 922 A1 relates to a receiving coil system in which the holding device comprises a bracket which is secured to a patient table and allows adjustable positioning of the receiving coils.
None of these known solutions offers a complete solution to the problems mentioned in the introduction. In particular the use of the distance sensors in the automatic shape adjustment of local coils should be regarded as disadvantageous since this requires additional signal detection and forwarding inside the magnetic resonance device, and this can only be achieved in a manner compatible with magnetic resonance with great effort and therefore harbors the risk that the magnetic resonance measurement as such will be disrupted.
Embodiments of the invention is therefore based on the object of disclosing a positioning and shaping method for local coils, which is improved compared with the above methods and in particular manages without the use of distance sensors.